To understand the surface evolution and potential habitability of other planets we must analyse their geology - the 3D structure and chemistry of the rocks that are exposed at the surface. Although rovers capture this 3D structure using stereo camera systems and other instruments, when we present this information to mission scientists for analysis it is generally confined to the 2D plane of a computer screen, and the spatial information is lost at the point when it is needed most. To address this problem, we design, develop, and evaluate a prototype Virtual Environment to present geological data in the 3D form in which it was originally captured, and users are supplied with a toolkit for measurement and annotation of data. We observed that users were inspired by the environment and felt more connected to it because they could move within the data; they valued the tools but did not trust the scale and therefore did not always trust the results. We conclude with recommendations for others working in this application area, and pose a series of questions for future research.